As necessitated by the function, water wheels have a relatively low rotational speed with a high torque or rotational moment. Therefore it is typical for the generation of current, to connect a multi-stage mechanical gearing with a shaft stub of the water wheel, and to connect an output shaft of the gearing with a generator via a transmission.
When there are changing water quantities, especially with an increase of the water quantity, the power and the torque are increased, so that the water wheel shaft and the gearing must take up relatively high peak torques.
In practice, therefore, the design of the parts is carried out with a factor of three relative to the normal loading. Thereby, relatively heavy and expensive structural components arise.
These known arrangements have a reduced efficiency, especially due to the mechanical transmission losses. Furthermore, the movable parts are subject to wear and require a complex or costly maintenance.